Blown film is preferable over cast film where high strength films are required. Linear low density polyethylene (LLDPE) and linear ultra low density polyethylene (LULDPE) are the most suitable for blown stretch film. However, for commercial applications, in the stretch wrapping industry, neither blown LLDPE nor blown LULDPE film has enough peel cling strength when stretched to 200 percent elongation, the commercially acceptable amount of stretching commonly required in stretch wrapping processes. Propylene polymer cling additives have been blended with LLDPE to provide monolayer blown stretch wrap film having commercially adequate cling at 200 percent elongation. The term "commercially adequate cling" is hereinafter defined as a peel cling strength of at least 100 g/2.54 cm, for convenience and clarity.
Multilayer blown stretch film is more versatile than monolayer film for many purposes. In an A/B/A or A/N/B/C type multilayer film, the core layer is typically about 80 weight percent of the film, with each of the two skin layers making up about 10 weight percent of the film.
Blown LLDPE and LULDPE have been found to be inadequate skin layers in multilayer stretch wrap film. They do not provide enough peel cling strength when the multilayer film is stretched to 200 percent elongation. Propylene polymer cling additives have been blended with LLDPE for use in multilayer blown stretch film. However, LLDPE skin layers require a relatively high concentration of propylene polymer cling additive to be effective.
In light of the above, it would be desirable to provide a new blown film composition suitable for use in making both monolayer blown stretch cling film and multilayer blown stretch cling film. It would be further desirable if a stretched multilayer film comprising a skin layer formed from such new composition would provide adequate cling.